Apparatus for continuous production of a helically corrugated metal tube

ABSTRACT

An apparatus for continuous production of a helically corrugated metal tube ( 12, 14 ) includes a corrugator head ( 11 ), which is driven by a rotary drive and is freely rotatably supported eccentrically to the longitudinal axis of the metal tube ( 12, 14 ). The corrugating tool ( 16 ) includes at least one disk whose eccentric position relative to the longitudinal axis of the metal tube ( 12, 14 ) is adjustable and whose circumferential surface rolls off the metal tube ( 12, 14 ).

[0001] This application is based on and claims the benefit of German Patent Application No. 10126399.6 filed May 31, 2001, which is incorporated by reference herein.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to an apparatus for continuous production of a helically corrugated metal tube in accordance with the preamble of claim 1.

[0003] German Examined Application DE 1 086 314 A discloses an apparatus for corrugating the sheath of an electrical cable, which provides for a rotatable annular corrugating tool through the opening of which the cable is guided. The axis of the corrugating tool is laterally offset relative to the sheath axis. The sum of this offset and the outer radius of the uncorrugated sheath is greater than the radius of the opening of the corrugating tool. The axis of the annular corrugating tool is inclined relative to the sheath axis. The corrugating tool is supported in a bearing that allows it to rotate around its own axis. The bearing is supported in a corrugator head, which is driven by a rotary drive and which rotates around the sheath axis.

[0004] In this prior art apparatus, the inner surface of the corrugating tool rolls off the sheath and due to its eccentric support in the corrugator head produces a corrugation in the sheath. The corrugating tool contacts the sheath over only a short arc. The friction between the corrugating tool and the sheath is rolling friction.

[0005] The deformation rib of the corrugating tool is subject to strong mechanical stresses during the corrugating process. Particularly if deeply corrugated tubes are being produced, the wall thickness of the deformation rib may therefore not fall below a certain size.

SUMMARY OF THE INVENTION

[0006] The object of the present invention is to improve the apparatus of the above-described type in such a way that it can be used to produce tubes with a small corrugation pitch, particularly tubes whose outside diameter measures less than 6 mm.

[0007] This object is attained by the features set forth in the characterizing portion of claim 1.

[0008] According to a particularly advantageous embodiment of the inventive apparatus, two or more disk-shaped corrugating tools are arranged within the corrugator head so as to be distributed over the circumference. The disks inside the corrugator head can be spaced at an axial distance from one another such that each disk dips into the corrugation valley that is produced by the disk in front of it and each subsequent disk enlarges the corrugation depth.

[0009] On the other hand, several disks may also be arranged in such a way that they produce a multiple-start helical corrugation.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The invention will now be explained in greater detail with reference to exemplary embodiments schematically depicted in the figures, wherein:

[0011]FIG. 1 shows a side elevation of a line for producing an optical fiber that is made of plastic and is surrounded by a corrugated metal tube; and

[0012]FIG. 2 illustrates a corrugating unit according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0013] With reference to FIG. 1, the plastic optical fiber 2 is continuously supplied from a supply reel 1. A metal strip M, preferably a copper strip, is supplied from a strip reel 3 and is cleaned in a cleaning unit 4. In a forming unit 5 comprising a plurality of forming steps, which are not identified in further detail, the metal strip M is then formed into an open seam tube surrounding the optical fiber 2. The longitudinal open seam is welded in a welding unit 6. The inside diameter of the welded tube is slightly larger than the outside diameter of the optical fiber 2 so that the welding heat does not affect the plastic optical fiber 2. If a laser welding device is used as welding unit 6, the strip cleaning unit 3 may be eliminated. A pull-off collet 7 transports the welded tube together with the optical fiber 2 through the line in the direction indicated by the arrows. The pull-off collet 7 has a plurality of clamping jaw pairs 7 a that encircle the welded tube in pincer-like fashion. The clamping jaw pairs 7 a are mounted to an endless chain 7 b, which is driven by an electric motor in a manner not depicted.

[0014] Arranged behind the pull-off collet 7 as seen in traveling direction is the corrugating unit 8 in which a corrugated metal tube, the corrugation valleys of which sit tightly against the optical fiber, is produced from the smooth metal tube.

[0015] The optical fiber 2 provided with the corrugated metal tube is finally wound onto a cable drum 9. A dancer arrangement 10 controls the take-up rate of the cable drum 9.

[0016] Finally, a plastic outer jacket may be extruded onto the corrugated metal tube in a manner not depicted.

[0017] The corrugating unit 8 will now be described in greater detail with reference to FIG. 2.

[0018] The corrugating unit 8 consists of the corrugator head 11, which is driven by a motor (not depicted), e.g. a hollow shaft motor, around the longitudinal axis of the smooth tube 12 to be corrugated. Inside the corrugator head 11 a housing 13 is arranged. This housing has a first opening 13 a through which the smooth tube 12 is guided and a second opening 13 b through which the corrugated tube 14 is guided. The corrugating tool 16, which is freely rotatably supported on a pin 17 fixed inside housing 13, is installed in a recess 15. The housing 13 in corrugator head 11 is arranged in such a way that it can be swiveled around an axis B, so that the axis of rotation A of the corrugating tool 16 extends at an angle relative to the longitudinal axis of the metal tube 12 or 14. The corrugating tool 16 is a disk that rotates around the smooth tube 12. To provide the smooth tube 12 with a corrugation, the housing 13 together with disk 16 is displaced in the direction of the smooth tube 12. As the corrugator head 11 rotates, the circumferential surface of disk 16 rolls off the surface of tube 12 and thereby produces a helically extending corrugation.

[0019] To displace the housing 13 in the direction of axis B as well as to rotate the housing 13 around axis B, screws 18, 19 and 20 are first loosened. By rotating the threaded nut 21, housing 13, which is provided with a threaded rod 22, is displaced in the direction of axis B and the desired corrugation depth is thereby adjusted.

[0020] After loosening nut 23, the degree of swivel of the housing 13 around axis B can be precisely adjusted by rotating element 24, which is connected to housing 13 via a bolt 25. By swiveling housing 13 around axis B, the pitch of the helical corrugation is optimally adjusted in relation to the take-up rate. After housing 13 has been precisely adjusted, the nuts 23, 18, 19 and 20 are retightened.

[0021] During the corrugation process, there is rolling friction between the circumferential surface of the disk 16 and the tube wall, so that the tube surface is not damaged. To increase the service life of the disk 16, at least the circumferential surface of the disk is hardened. 

What is claimed is:
 1. An apparatus for continuous production of a helically corrugated metal tube, comprising a corrugator head driven by a rotary drive in which a corrugating tool is freely rotatably supported eccentrically to the longitudinal axis of the metal tube, characterized in that the corrugating tool (16) includes at least one disk whose eccentric position relative to the longitudinal axis of the metal tube (12, 14) is adjustable and whose circumferential surface rolls off the metal tube (12, 14).
 2. An apparatus as claimed in claim 1, characterized in that the axis of rotation A of the disk extends at an angle to the longitudinal direction of the metal tube (12, 14).
 3. An apparatus as claimed in claim 1, characterized in that the disk is freely rotatably supported in a housing (13) having a passage opening for the metal tube (12, 14), and that the housing (13) can be displaced inside the corrugator head (11) in the direction of the metal tube (12, 14) and swiveled around an axis B extending perpendicularly to the longitudinal axis of the metal tube (12, 14).
 4. An apparatus as claimed claim 1, characterized in that at least the circumferential surface of the disk is hardened.
 5. An apparatus as claimed in claim 1, characterized in that the housing (13) is displaced by at least one threaded spindle that is guided through the wall of the corrugator head (11). 